The present invention relates generally to hoses and particularly to fuel transport hoses such as fuel filler and fuel filler neck hoses having reduced permeability to fuel vapors. More particularly, this invention relates to blends of fluorelastomer interpolymers with fluorothermoplastic interpolymers, and to the use of such blends as a barrier layer for fuel transport hoses to reduce the permeability of such hoses to fuel vapors.
Recent environmental regulations imposed on the automotive industry severely limit the amount of fuel vapor that can permeate from the fuel systems of motor vehicles. Choosing the right polymer to provide high performance, long service life, and reduced permeability of fuel in the fuel systems of motor vehicles while maintaining costs at an acceptable level has been more difficult for automotive designers than ever before. Typically, fuel transfer and fuel vapor hoses have been made of butadiene-acrylonitrile rubber as the tube, but such hoses have a high permeability to fuel. Other hoses have a fluoroelastomer as the inner wall surface layer of the hose, but such hoses have higher permeability to fuel vapors. Attempts to produce fuel transfer hoses with reduced permeability to fuel vapors have included the use of corrugated polyamide and fluorocarbon thermoplastic tubes. However, these structures are very expensive.
Other attempts to produce a fuel filler neck hose with reduced permeability to fuel vapors used a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride terpolymer liner and a thicker layer of hexafluoropropylene-vinylidene fluoride copolymer or other suitable elastomer as the conductive inner part of the tube. See, for example, U.S. Pat. Nos. 4,606,952 to Sugimoto and 5,430,603 to Albino et al. Such hose structures have a tendency to wrinkle on the inner radius of the forming mandrel or pin causing a cosmetic defect.
Accordingly, there is a need for an improved fuel hose that meets present industry standards.